SAN FRANCISCO  The association representing shipping lines decided Friday to lock out longshoremen at all West Coast ports until Sunday morning as contract negotiations deteriorated.

The 36-hour cooling-off period, which will immediately curtail the flow of goods across the nation, was announced after the Pacific Maritime Association accused the longshoremen's union of slowing down the pace of work as a tactic to gain leverage in increasingly acrimonious talks.

The association's board met Friday morning and unanimously agreed to shutter the ports, according to president Joseph Miniace. The lockout was scheduled to begin Friday evening.

Mr. Miniace called it a very, very tough decision, but one that the association had to make because the union was bargaining in bad faith.

It's the very last thing we wanted to do, Mr. Miniace said. But the union forced us into this.

A spokesman for the International Longshore and Warehouse Union said that union negotiators wanted to keep talking. The union learned of the lockout Friday morning from association negotiators when the two sides met for talks.

Miniace showed the same disrespect for the union he has since the beginning of these talks, union president James Spinosa said. He is unilaterally taking the action of closing all ports and bears full responsibility for its effects on the American economy.

The disruption could stanch the flow of products from Asia just as importers are rushing to distribute goods for the holiday season. The association has said that a coastwide labor disruption could cost the U.S. economy around $1 billion per day. The ports handle more than $300 billion in imports and exports each year.

At this point we are hopeful the two parties will come back to the bargaining table in good faith, Department of Labor spokeswoman Sue Hensley said.

The crisis was foreshadowed Thursday evening when the association said longshoremen were slowing the pace of work at ports in Los Angeles, Oakland, Portland, Ore; Seattle and Tacoma, Wash.

The union had issued a directive earlier Thursday telling the 10,500 workers it represents at all 29 major Pacific ports to work in strict accordance with all safety and health rules.

The association has consistently said that if it determined workers were slowing down their pace on purpose, there would be a lockout.